More particularly, although not exclusively, the present invention is applicable to a turntable or rotary plate that is intended for precision positioning applications (such as inspection of semiconductor wafers, metrology, positioning of components, and microrobotics) in different fields, including research, industry, and defence.
Generally, a device of this kind for driving in rotation a toothed wheel usually includes the following:                a worm that is designed to mesh with said toothed wheel; and        a motor, a drive shaft of which is connected, via a belt, to a first extremity of said worm in order to drive the worm in rotation. In addition, this motor is fixed relative to said worm.        
Furthermore, in particular to make it easier to position the worm in mesh with the toothed wheel, this device for driving in rotation can also include:                a flexible sleeve that surrounds the worm; and        a pre-stressing means that can be adjusted by an operator and that enables pressure to be exerted on the sleeve at a second extremity of the worm opposite said first extremity, the purpose being to apply the worm appropriately against the toothed wheel.        
However, the pressure exerted on the flexible sleeve by this prestressing means is disrupted by the belt tension being exerted at the other extremity in such a way that the prestressing means cannot perform its function effectively. This disruption can lead to difficulties in fitting and reduce the stability of positioning of the assembly during operation.
This standard drive device is therefore not completely satisfactory.